This invention relates to floating equipment, or float apparatus, used in cementing operations and to methods of using such equipment. More particularly, this invention relates to an improved float apparatus that has a deformable valve element that will engage and seal against a valve body.
Typically, after a well for the production of oil and/or gas has been drilled, casing will be lowered into and cemented in the well. The weight of the casing, particularly with deep wells, creates a tremendous amount of stress and strain on the equipment used to lower the casing into the well. In order to minimize that stress, floating equipment, such as, but not limited to, float shoes and/or float collars, is used in the casing string.
The float equipment typically consists of a valve affixed to the outer casing which allows fluid to flow down through the casing but prevents flow in the opposite direction. Because upward flow is obstructed, a portion of the weight of the casing will float or ride on the well fluid thus reducing the amount of weight carried by the equipment lowering the casing into the well. Once the casing is in position, cement is flowed down through the inner diameter of the casing, through the valve and into the annular space between the outer diameter of the casing and the wellbore. After the cement job is complete, the valve keeps the cement below and behind the casing string.
The float equipment is typically fabricated by affixing a check valve in an outer sleeve which is adapted to be threaded directly into a casing string. The check valve generally includes a valve body and a poppet disposed in the valve body. The valve body defines a valve seat, and the valve poppet is urged into engagement with the valve seat to prevent flow through the valve body in one direction. An elastomeric seal, typically referred to as a lip seal, is generally positioned between the valve poppet and the valve body to provide sealing engagement. The present invention provides improved methods and apparatus for providing a seal in float apparatus.
The float apparatus of the present invention provides an efficient way in which to seal to prevent upward flow through the float apparatus. Float equipment, or float apparatus, as referred to herein may include any device referred to in the industry as float equipment or float apparatus, such as but not limited to float collars and float shoes. Generally, float apparatus includes an outer case, or outer sleeve with an outer surface and an inner surface. The inner surface of the outer sleeve defines a central opening, or flow passage. The check valve is disposed in the outer sleeve. The check valve includes a valve body, or valve housing which has an outer surface and an inner surface. The valve body defines a central opening communicated with the flow passage of the outer case. The valve body is fixedly attached to the outer case with a body portion. The body portion fills an annulus between the outer case and the valve body, and may be comprised of high compressive strength cement.
The float apparatus also includes a valve element that is sealingly engageable with the valve body. Preferably, the valve element is sealingly engageable with a valve seat defined on the valve body. The valve element is a deformable valve element that will conform to the shape of and thus seal against the valve seat defined by the valve body. Preferably, the valve seat has a first seat portion which may be cylindrically shaped, and a second seat portion that tapers radially inwardly from the first seat portion and may be frustoconically shaped. The valve element is connected to a valve stem which is movably disposed in a valve guide that is disposed in the valve body central opening and connected to the valve body. The valve element may be comprised of a thermoplastic material and is preferably comprised of a glass-filled NYLON. The valve element is more preferably comprised of a 33% glass-filled NYLON. The valve body likewise may be comprised of a thermoplastic material. The valve body is preferably comprised of a glass-filled NYLON and more preferably of a 33% glass-filled NYLON. The invention includes a biasing means that will urge the valve element into engagement with the valve seat by applying a force in a first, or upward, direction to move the valve element into engagement with the valve seat. Additional force in the upward direction causes the valve element to move from the first seat portion to the second seat portion and to seal against the second seat portion. The first direction referred to herein is the upward direction and the second direction is the downward direction. It will be understood that upward means toward the surface and that downward means toward the bottom or terminating end of the wellbore in which the float apparatus will be positioned.